This book highlights recent progress in the development of small-molecule inhibitors of oncogenic transcription factors and is relevant for postgraduates, researchers and practitioners.

With the critical role of aberrantly active Signal Transducer and Activator of Transcription (Stat) 3 protein in many human cancers, selective small-molecule inhibitors targeting the dimerization event which is required for stat3 activation, would be valuable as therapeutic agents. And the inhibitors will be useful chemical probes to clarify the complex biological functions of Stat3. By computational and structural analyses of the interaction between Stat3 and the lead dimerization disruptor, S3I-201, we have designed a diverse set of analogs. One of the most active analogs, S3I-201.1066 is derived to contain a cyclo-hexyl benzyl moiety on the amide nitrogen, which increases the binding to the Stat3 SH2 domain. Evidence is presented from in vitro biochemical and biophysical studies that S3I-201.1066 directly interacts with Stat3 or the SH2 domain, with an affinity (K[subscript D]) of 2.74 [micrometer], and disrupts the binding of Stat3 to the cognate pTyr-peptide, GpYLPQTV-NH2, with an IC50 of 23 [micrometer]. Moreover, S3I-201.1066 selectively blocks the association of Stat3 with the epidermal growth factor receptor (EGFR), and inhibits Stat3 tyrosine phosphorylation and nuclear translocation in EGF-stimulated mouse fibroblasts. In cancer cells that harbor aberrant Stat3 activity, S3I-201.1066 inhibits constitutive Stat3 DNA-binding and transcriptional activities.

The constitutive activation of Stat3 is frequently detected in human breast cancer cell lines as well as in clinical breast cancer specimens and may play an important role in oncogenesis of breast carcinoma. Activated Stat3 may participate in oncogenesis by stimulating cell proliferation, promoting tumor angiogenesis, and resisting to apoptosis. Hence, Stat3 represents an attractive target for cancer therapy. In this study, of the nearly 429,000 compounds screened by virtual database screening, chemical samples of top 100 compounds identified as candidate small molecule inhibitors of Stat3 were evaluated using Stat3-dependent luciferase reporter as well as other cell-based assays. Through serial functional evaluation based on our established cell-based assays, one compound, termed Sta-21 inhibits Stat3 DNA binding activity, Stat3 dimerization, and Stat3-dependent luciferase activity. Moreover, Sta-21 reduces the survival of breast carcinoma cells with constitutive Stat3 signaling but has minimal effect on the cells in which constitutive Stat3 signaling is absent. Together, these results demonstrate that Sta-21 inhibits breast cancer cells that express constitutive active Stat3. Sta-21 may have a therapeutic potential to be developed as a new class of anti-cancer drug for the treatment of human cancer with activated Stat3.

Abstract: Signal transducer and activator of transcription 3 (STAT3) is one of the downstream signaling proteins for cytokine and growth factor receptors. Receptor activation induces tyrosine phosphorylation leading to dimerization of two STAT monomers by reciprocal phosphotyrosine-SH2 interactions. This dimer translocates into the nucleus where it controls the transcription of several apoptosis and cell cycle-regulatory proteins. STAT3 has been identified to be overexpressed in many different kinds of blood malignancies and solid tumors. Inhibition of STAT3 dimerization stops translocation into the nucleus and induces apoptosis. Several novel small molecules have been synthesized using a structural-based strategy with an aim to specifically inhibit STAT3 dimerization and have been examined for their antiproliferative activity on breast, pancreatic, prostrate and brain cancer. Among the compounds synthesized, LLL-3, LLL-6 and LLL-12 were found to be active against various cancer cell lines. LLL-12 was found to be the most potent analogue among the LLL series of compounds and even more potent than known inhibitors against various cancer cells overexpressing STAT3, and it did not inhibit STAT1. LLL-12 was also found to reduce tumor growth. Arginine methylation is an important post-translational modification which mainly occurs in nuclear proteins and is involved in structural remodeling of chromatin, signal transduction, cellular proliferation, gene transcription, translation, DNA repair, apoptosis, RNA processing, and mRNA splicing. PRMT5 has been shown to catalyze the formation of monomethylargininie (MMA) and symmetric dimethylarginine (sDMA) on a variety of substrates including myelin basic protein (MBP), the Sm ribonucleoproteins, and additional proteins that require symmetric dimethylarginine residues. PRMT5 has been shown to methylate histones H2A, H3 and H4. PRMT5 has been reported to be associated with tumors. PRMT5 overexpression has been documented in multiple non-Hodgkin's lymphoma cell lines and primary mantle cell lymphoma tumor samples. Molecular docking was used to screen a library of 10,000 compounds to identify 8 potential compounds for biological screening. Subsequent screening identified BLL-1 as our lead compound which was further modified using traditional medicinal chemistry approaches and molecular modeling. BLL-1 was the most potent compound tested on JeKo and Mino cells. Survivin is a 142 amino acid and is the smallest member of the IAP family. Survivin indirectly acts on caspases by associating with cdk4 resulting in release of p21Cip1/Waf1, which interacts with procaspase-3 to suppress Fas mediated cell death. 163 Survivin also provides cytoprotection to cells against caspase-independent cell death by inhibiting the AIF pathway. Survivin is present on the mitotic machinery of dividing cells and regulates cell division. Survivin has been shown to be overexpressed in cancer. Lack of Survivin or disruption of the Survivin function would be expected to cause apoptosis in tumor cells. Structural study of compound 2 showed that its binding site is located at the dimerization interface. Compound 2 was modified with an aim to target the Survivin binding site. LLP-3 was found to be active at 50 um against various cancer cell lines. LLP-3 also delayed mitosis and cells appeared to lose viability after being exposed to LLP-3 for 48 hours.

An expert guide to targeting protein kinases in cancer therapy Research has shown that protein kinases can instigate the formation and spread of cancer when they transmit faulty signals inside cells. Because of this fact, pharmaceutical scientists have targeted kinases for intensive study, and have been working to develop medicinal roadblocks to sever their malignant means of communication. Complete with full-color presentations, Targeting Protein Kinases for Cancer Therapy defines the structural features of protein kinases and examines their cellular functions. Combining kinase biology with chemistry and pharmacology applications, this book enlists emerging data to drive the discovery of new cancer-fighting drugs. Valuable information includes: Comprehensive overviews of the major kinase families involved in oncology, integrating protein structure and function, and providing important tools to assist pharmaceutical researchers to understand and work in this dynamic area of cancer drug research Focus on small molecule inhibitors as well as other therapeutic modalities Discussion of kinase inhibitors that have entered clinical trials for the treatment of cancer, with an emphasis on molecules that have progressed to late stage clinical trials and, in a few cases, to market Providing a platform for further study, this important work reviews both the successes and challenges of kinase inhibitor therapy, and provides insight into future directions in the war against cancer.

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in malignant tumors, and its activation is associated with high histological grade and advanced cancer stage. STAT3 has been shown to play important roles in multiple aspects of cancer aggressiveness including proliferation, survival, self-renewal, migration, invasion, angiogenesis and immune response by regulating the expression of diverse downstream target genes. Thus, inhibiting STAT3 promises to be an attractive strategy for treatment of advanced tumors with metastatic potential. We firstly identified a STAT3 inhibitor, inS3-54, by targeting the DNA-binding site of STAT3 using an in-silico screening approach; however, inS3-54 was finally found not to be appropriate for further studies because of low specificity on STAT3 and poor absorption in mice. To develop an effective and specific STAT3 inhibitor, we identified 89 analogues for the structure-activity relationship analysis. By using hematopoietic progenitor cells isolated from wild-type and STAT3 conditional knockout mice, further studies showed that three analogues (A18, A26 and A69) only inhibited STAT3-dependent colony formation of hematopoietic progenitor cells, indicating a higher selectivity for STAT3 than their parental compound, inS3-54. These compounds were found to (1) inhibit STAT3-specific DNA binding activity; (2) bind to STAT3 protein; (3) suppress proliferation of cancer cells harboring aberrant STAT3 signaling; (4) inhibit migration and invasion of cancer cells and (5) inhibit STAT3-dependent expression of downstream targets by blocking the binding of STAT3 to the promoter regions of responsive genes in cells. In addition, A18 can reduce tumor growth in a mouse xenograft model of lung cancer with little effect on body weight. Taken together, we conclude that it is feasible to inhibit STAT3 by targeting its DNA-binding domain for discovery of anticancer therapeutics.

Das umfassende Referenzwerk zur Kinase-Forschung: Ausführlich werden die Themen Kinase-Engineering, Peptidsubstrat-Engineering, das Design von Co-Substraten und Kinasehemmer erläutert sowie deren Anwendung in der Bio- und Pharmaforschung beschrieben.

This book describes the challenges involved in developing mTOR inhibitors for cancer treatment, starting with an in-depth examination of their molecular mechanism of action, with emphasis on the class side-effects, efficacy and mechanisms of resistance, as well as on promising novel directions for their development, including novel compounds and rational combinations with other anti-neoplastic drugs. Over the last 10 years, inhibitors of mTOR have emerged as a major class of anticancer drugs. Two rapamycin analogs are currently approved for the treatment of renal cell carcinoma, and it is estimated that a variety of other tumor types could benefit from mTOR inhibition, with numerous clinical trials (including pivotal registration trials) already underway. Second-generation small-molecule inhibitors of the pathway have also shown promise in terms of their superior tolerability and efficacy and are undergoing extensive clinical evaluation, with an estimated 30+ compounds currently under evaluation.